Electric resistance unit.



H. W. DENHARD.

ELECTRIC RESISTANCE UNIT.

APPLICATION FILED 001.31, 1911.

1,102,249. Patented July 7, 1914.

2 SHEETS-SHEET 1.

H. W. DENHARD.

ELECTRIC RESISTANCE UNIT.

APPLIGATION FILED 00T. 31, 1911.

Patented July 7, 1914.

2 SHEETS-SHEET 2.

NI'IED sTArEs rA-r lorricnl.

HARRY W. DENHARD, or'SAN FRANCISCO, CALIFORNIA, ASSIGNon 'ro 'r1-IE cUfrLI-zrf HAMMER atraco., or MILWAUKEE, WISCONSIN, A conronATIoN or WISCONSIN.

ELECTRIC RESISTANCE UNIT.

. Specification or Letters Patent.

' y Patented July 7, i914.

` 'Application ined. Meuterei, Ian. 'serian No. esame.

1'0 all 'whom it may concernn Beit known that I, HARRYi W. D'ENHARD, a citizen ofthe United' States, residing at San Francisco, i-n\the county of San Francisco and State of California, have invented new and useful Improvements in Electric ,Resistance Units, of which vthe following is aV full, clear, concise, and exact description, reference being had to the accompanying drawing, forming a part o'this-specification. My invention ance units?.

It has among its objects to lprovide an im'- proved electric resistance unit.

A further object' of my invention is to provide yanl improved electric heatingl device which is capable of being made up into liat form and used asa radiant heater, theheat waves being-directly radiated to the object to be heated., Other objectsand'wadvantages ofA my inil proved construction will hereinafter appear. In, the accompanying drawings-I have tor' relates toI electric resist- Y purposes of illustration shown one. form v.which my invention'may assume in practice. My invention is not, however, v.lmnted to this form, ybut may assume other forms.`

In the views of'these drawings z Figure i llshovvsI a central sectional view thronghay heater. .FigL 2 shows a top plan-view on line 2-'2 'of Fig. `l, the cover being removed.

Fig. 43l Vshows* a sectional viewl on :line 3,--3

. of Fig. 2.y Fig. 4 shows abottomview of the heater. Fig. 5 shows' the top plate in elevation. Y

,In the construction shown for purposes of illustration l have illustrated an .electric l heater .of a disk type including a plurality of -radalextendingV arms upon the opposite sides ,of which a resistance material is woundl spirally; the whole being inclosed in a metallic casing including a top vplate hav-- l ing `slots inthe same and adapted to carry Vi5 the object to be heated,y and bottom platesY rarrzinged', to support the heating element in ,positlon and carry suitable'k terminal .connectionsjfor the samef,

The heating element l is "in" a' preferred vy form constructed vasshown .in Fig. 2, in-

` cluding an outer-ringlike frame-orband-l,`

a centralI hub 2 and'radial extending"arms` 3 fixed. infthehub andy at pdint's about the material.

-toward the outer edge-o1e the: arms.

periphery of the 'ring l.l ln a preferred formy the ring l. isformed of a stiff material the ends l-being interlitted as shown inFig. 2. if desired lf may use a metal ring. The

hub 2, Ina'y if desired, be made of asimilar material to that used for the ring. The

arms [3j are preferably tted .ina suitablemanner 1n both the hub 2 and the ring l, sothat theymay not be readily dislocated. llt a desired l may provide extensions 4 on the, ends ont' the arms .which extend throughthese members, l as shown for inst-ance in Fig. -2.. ln a preferred form the arms 3 are formed of \an insulating material. lf desired,`li may use mica AasI this insulating lin order to receive the resist-ance material thearms 2 are preferably slotted, as shownl at 5 in Fig. 1, the slots being ar,-v ranged on opposite sides of the arms and preferably extending a ,'.tride .diagonally illustrated in Fig. l., the shits on the opposite arms extend in 'opposite directions andv `are-preferably so arranged that a resistance material may `be Wound uponone edge f the arms in' ay Spiral and then brought back to the opposite ledge of the arms, upon which it is again wound in a spiral form. Theresista-nce material 6 may be of any desired form. lin a'preferred form, however, l use a single length of resistance'- )nire which is brought in at the side of the instance at a binding post' 7 .carried upon .a strip of insulating material Stextending between the ends of two adjacent arms 3. lf

' desired,the strip 8`ma likewisebemade of 'mica ln a l preerre length of resistance-,mrc 1spassed around .form the enterino' theinner shank of the binding screw and 4is then brought out to the first yslot 5, which in this instance is illustrated -as the' first 'slot in the llower adjacent arm 3., From this notch the wire/ is then preferably Wound successively around the unit in a spiral form," passing the first notch 5 previously mentioned Vin the second notch on the same arm and-being successively ybrought toward the center 'of the -unit,. where, at the,I inner no-tchl 5 .on the arm at' theopposite/side of'the binding post, the Wire is-passed on the underside of the irstmentioned arm,Y from which it is again wound spirally from unit, las ier' downward to the lirst notch vided in series or in yrahty of heats.l

the center of the device to the outside of the same and then brought out at the other binding screw 8. It is obvious that if desired I may so connect these several coils parallelas to provlde a plu- While ina preferred form I use a'single length of resista ce material, I may, if desired, use a plurality of lengths of resistance material, the lengths being connected to each other in a suitable manner at any desirable point. In a preferred form in order to hold the resistance material snugly within the notches, I preferably fill these notches with asuitable insulating material, as shown in Fig. l. In a preferred form 'the junctionof the arms with the hub member 2is preferably covered with a similar insulating material, which, if desired, may be first made up in the form of paste or applied to the hub, upon which it then hardens. By the provision of this insulating covering for the hub- I am able to provide a unit of great strength on account of the metallic frame, and at the same time provide a unit in which there is no danger of short cireuiting due to the provision of the insulation.V In a preferred form the heating -element is inclosed in a metallic casing including a metallic cover plate 10, an under supported plate 11 and a bottom plate 12, the unit and the several plates being positioned upon a suitable central bolt or screw 13. The cover plate 10 is preferably provided with a gridlike top having corrugations 14 formed therein, in which the upwardly extending corrugations are preferably provided .with slots 15 extending substantially across the upper surface of the same. It is thus seen that a grid-like surface is provided on the plate. In a preferred form the plate 10 is also provided with a flange 16 which extends around the unit and serves to house the same. The unit is preferably held in position snugly against the inner surface of the plate 10 by means of the plate 11, which is preferably provided with a raised or convex center having'a central perforation Within the same, through which the bolt 13 extends. The plate 11 is also preferably provided with an outer' ange 17 around its periphery, 'which serves to support the outer edge of theunit and is preferably provided with .extensions 18 which extend beneath the edge of the ring 1 and serve to support the same. In a preferred form the platell is also pro- With a substantiallyrectangular shaped opening on one side of the Samenbetvveen the flange 18 and the central opening. In this opening is housed in a preferred form the reduced end of an insulating block 19- having slots 20 formed therein, through which suitable leads 21 may extend from the binding posts 7 and plugs 22 preferably 9 to suitable terminal carried on the lower the plate` 12 is provided witfi surface of the plate 12. In a referred form a central recess 28 arranged to permit the bolt 13 to pass through the same and to receive the lower end of a spacing sleeve 24, which is preferably fitted around ,the bolt 13 between the plate 12 and the plate 11, as shown in Fig. 1. In a preferred form the bolt 14 is seated in a suitable central opening in the plate 10 and extends down through the hub of the heating unit, the opening in the plate 11, the sleeve 24 and the'plate1'2, being-provided with a tap 25 on -its lower end which serves to hold the part-s Securely together. sired the upperA surface of the plate 1l,l adjacent to the insulating block 19 may be covered with a suitable insulation 26 in order to prevent any possibility of the short circuit ing of the device on the metallic plate. It is obvious that the leads 21- may be of any desired construction. However, in a preferred form I employ a Hat lead of the ribbon type, since I find that these may be read` ily made to give a good contact at the binding posts and may be readilyT brought down through the device in a small space and brought out to the binding screws 27 of the terminal members. l y my improved construction yI have provided'an lmproved electric resistance unit wherein the electric resistance wire is arranged 1n a compact form on a suitable frame so that it is eifectually insulated, and yet at the same time may develop a high'degrec of heat. Further, the device is such that the heat Waves may be readily radiated to an object to be heated. By my improved construction and arrangement of the resistance unit and the casing which incloses the same I have provided an exceedingly compact heater, which may be readily made up 1n a disk or other form and adapted to use as a stove or heater or in a Wide varietv of relations. Further the resistance element is securely and eifectually inclosed Within the unit in such a m`anner-as to be protected. Further the electrical connections for the device may be readily made andI are full protected Within the casing so that all that it is necessary for one to do who desires. to connect the device in circuit is to place an attachment plug upon the terminal members. It is obvious 'that theinclosed unit may be placed upon any suitable support or stand, or used in a Wide number of different relations. -By my improved construction I have provided a heating unit of increased efliciency in a very compact and rugged form, which may be very conveniently used in service for a long period andwhich'may also be readily and cheaply manufactured.

IVhile I have in this application described one ferm which my invention may assume in practice, I do not wish to be limited to the form shown for purposes of illustration, but

incanta wish rather to include within the scope ot carried on said strip.

this application all of those forms ot my invention falling within its spirit.

l/Vhat I claim as new and desire to secure by Letters Patent is as follows 1. In an electric resistance unit, a frame having a plurality of radially extending arms, and a resistance material engaging said arms and wound on the opposite sides thereof in tparallel planes;

2. In anv electric resistance unit, a frame, a plurality of'notched radially extendin -insulating strips having their ends attache to said frame, and a resistance materialwound on. opposite sides of said strips and resting in said notches. A

3. In an electric resistance unit, a ring, a hub, a plurality of notched radially extending arms attached to said ring andhub and a resistance material wound spirally in 0p- .posite directions` on Ithe opposite edges of said strips and passing through said notches.

45. In an electric resistance unit, a ring,

i a hub, a plurality of notched radially extending arms having extensions extending through said ring and said hub, a resistance material wound on the 'opposite edges of said arms and. passingthroughI said notches, an insulating strip connectmg certain of said radially extending arms, and binding lposts for said resistance material 5. In an electric resistance unit, a'ring, a hub, a plurality of radially extending arms having projections seated in said ring .and said hub and having notches in their wound on the opposite edges of said strips and passing through said notches, and an inclosing casing arranged to permit the radiant energy developed by sald unit to pass to the object to be heated.

7. In an electric heating device, a slotted cover plate having a depending flange and depressed portions between the slots, a heat ing unit housed'in said' late; a plate having a c'onvex surface an an upwardly extending lange for'positionin'g said unit in said cover plate, a bottom plate inclosing said last mentioned plate, means for holding the parts in assembled relation, and means for insulating'the line connections within said heating unit.

'In witness whereof, I have hereunto subscribed my name in the presence of two witnesses.

HARRY W. DENHARD. Witnesses:

lil. L. RocKwELL, Gro. B. JONES.

lso 

